title: Mitogenomic phylogenetic analyses of the Delphinidae with an emphasis on the Globicephalinae.
abstract: BACKGROUND
  Previous DNA-based phylogenetic studies of the Delphinidae family suggest it has undergone rapid diversification, as characterised by unresolved and poorly supported taxonomic relationships (polytomies) for some of the species within this group. Using an increased amount of sequence data we test between alternative hypotheses of soft polytomies caused by rapid speciation, slow evolutionary rate and/or insufficient sequence data, and hard polytomies caused by simultaneous speciation within this family. Combining the mitogenome sequences of five new and 12 previously published species within the Delphinidae, we used Bayesian and maximum-likelihood methods to estimate the phylogeny from partitioned and unpartitioned mitogenome sequences. Further ad hoc tests were then conducted to estimate the support for alternative topologies.
  
  
  RESULTS
  We found high support for all the relationships within our reconstructed phylogenies, and topologies were consistent between the Bayesian and maximum-likelihood trees inferred from partitioned and unpartitioned data. Resolved relationships included the placement of the killer whale (Orcinus orca) as sister taxon to the rest of the Globicephalinae subfamily, placement of the Risso's dolphin (Grampus griseus) within the Globicephalinae subfamily, removal of the white-beaked dolphin (Lagenorhynchus albirostris) from the Delphininae subfamily and the placement of the rough-toothed dolphin (Steno bredanensis) as sister taxon to the rest of the Delphininae subfamily rather than within the Globicephalinae subfamily. The additional testing of alternative topologies allowed us to reject all other putative relationships, with the exception that we were unable to reject the hypothesis that the relationship between L. albirostris and the Globicephalinae and Delphininae subfamilies was polytomic.
  
  
  CONCLUSIONS
  Despite their rapid diversification, the increased sequence data yielded by mitogenomes enables the resolution of a strongly supported, bifurcating phylogeny, and a chronology of the divergences within the Delphinidae family. This highlights the benefits and potential application of large mitogenome datasets to resolve long-standing phylogenetic uncertainties.
authors.affiliation: Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen, Denmark.
authors.forename: Julia T
authors.initials: JT
authors.lastname: Vilstrup
authors.forename: Simon Yw
authors.initials: SY
authors.lastname: Ho
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Foote
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Morin
authors.forename: Danielle
authors.initials: D
authors.lastname: Kreb
authors.forename: Michael
authors.initials: M
authors.lastname: Krützen
authors.forename: Guido J
authors.initials: GJ
authors.lastname: Parra
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Robertson
authors.forename: Renaud
authors.initials: R
authors.lastname: de Stephanis
authors.forename: Philippe
authors.initials: P
authors.lastname: Verborgh
authors.forename: Eske
authors.initials: E
authors.lastname: Willerslev
authors.forename: Ludovic
authors.initials: L
authors.lastname: Orlando
authors.forename: M Thomas P
authors.initials: MT
authors.lastname: Gilbert
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D004272:DNA, Mitochondrial / Q000235:genetics; D004289:Dolphins / Q000145:classification / Q000235:genetics*; D019143:Evolution, Molecular; D054629:Genome, Mitochondrial; D059014:High-Throughput Nucleotide Sequencing; D016013:Likelihood Functions; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial